SPECIFICATION LIBRARY
ASTM A325
ASTM A325 Specification Guide
Note: The specifications for A325 and A490 were integrated into the ASTM F3125 specification in 2016. This consolidation was part of an effort to streamline and simplify the standards for high-strength structural bolts, making it easier for industry professionals to specify and select fasteners for construction and engineering projects.
For more on the mechanical and chemical properties, please visit our ASTM F3125 Specification Guide.
Bolt Specifications (ASTM A325)
| Specification | Details |
|---|---|
| Diameter Range | 1/2" to 1-1/2" |
| Thread Type | Unified National Coarse (UNC) |
| Thread Length | Bolts up to 6" long: 2× diameter + 1/4". Bolts longer than 6": 2× diameter + 1/2". |
| Head Style | Heavy hex head |
| Material | Medium carbon steel, quenched and tempered |
| Tensile Strength | 120,000 psi min (diameters up to 1") |
| Proof Load | 85,000 psi (diameters up to 1") |
| Yield Strength | 92,000 psi min (diameters up to 1") |
| Surface Finish | Plain, hot-dip galvanized, mechanically galvanized, or zinc plated |
| Markings | Manufacturer's identification and grade symbol on head |
| Nut Compatibility | ASTM A563 DH heavy hex nuts (A194 2H also acceptable) |
| Washer Compatibility | ASTM F436 hardened steel washers |
| Applications | Structural steel connections, bridge construction, heavy machinery |
Dimensions for ASTM A325 Bolts
Note: These are nominal dimensions, for complete dimensional data with tolerances— please see the ASME B18.2.6 specification in full.
| Diameter (inches) | Thread Pitch (threads per inch) | Head Width Across Flats (inches) | Head Height (inches) | Min. Thread Length (inches) | Tensile Strength (psi) |
|---|---|---|---|---|---|
| 1/2 | 13 | 7/8 | 21/64 | 1-1/4 | 120,000 |
| 5/8 | 11 | 1-1/16 | 27/64 | 1-3/8 | 120,000 |
| 3/4 | 10 | 1-1/4 | 1/2 | 1-1/2 | 120,000 |
| 7/8 | 9 | 1-7/16 | 37/64 | 1-5/8 | 120,000 |
| 1 | 8 | 1-5/8 | 43/64 | 1-3/4 | 120,000 |
| 1-1/8 | 7 | 1-13/16 | 3/4 | 1-7/8 | 105,000 |
| 1-1/4 | 7 | 2 | 27/32 | 2 | 105,000 |
| 1-3/8 | 6 | 2-3/16 | 15/16 | 2-1/4 | 105,000 |
| 1-1/2 | 6 | 2-3/8 | 1 | 2-1/2 | 105,000 |
Length Tolerances
Length tolerance (inches) by nominal diameter
| Nominal Length | Nominal Diameter | |||
|---|---|---|---|---|
| 1/2" | 5/8" | 3/4" – 1" | 1-1/8" – 1-1/2" | |
| Up to 6" | −0.12 | −0.12 | −0.19 | −0.25 |
| Over 6" | −0.19 | −0.25 | −0.25 | −0.25 |
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